A Cu-Only Superoxide Dismutase From Stripe Rust Fungi Functions As A Virulence Factor Deployed For Counter Defense Against Host-Derived Oxidative Stress

Plants quickly accumulate reactive oxygen species (ROS) to resist against pathogen invasion, while pathogens strive to escape host immune surveillance by degrading ROS. However, the nature of the strategies that fungal pathogens adopt to counteract host-derived oxidative stress is manifold and requires deep investigation. In this study, a superoxide dismutase (SOD) fromPuccinia striiformisf. sp.tritici(Pst) PsSOD2 with a signal peptide (SP) and the glycophosphatidyl inositol (GPI) anchor, strongly induced during infection, was analysed for its biological characteristics and potential role in wheat-Pstinteractions. The results showed thatPsSOD2encodes a Cu-only SOD and responded to ROS treatment. Heterologous complementation assays inSaccharomyces cerevisiaesuggest that the SP of PsSOD2 is functional for its secretion. Transient expression inNicotiana benthamianaleaves revealed that PsSOD2 is localized to the plasma membrane. In addition, knockdown ofPsSOD2by host-induced gene silencing reducedPstvirulence and resulted in restricted hyphal development and increased ROS accumulation. In contrast, heterologous transient assays ofPsSOD2suppressed flg22-elicited ROS production. Taken together, our data indicate that PsSOD2, as a virulence factor, was induced and localized to the plasma membrane where it may function to scavenge host-derived ROS for promoting fungal infection.